Hydraulic turbo-couplings



March 1, 1966 J, BECKER 3,237,409

HYDRAULIC TURBO-COUPLINGS Filed April 6, 1964 2 Sheets-Sheet 1 2H 28 3| 342740 e 47 FIG. I 9 2s i. s 3e I 37 43 IO 2a u ---|7 l2 v I 'w-b-.i-.v- I s INVENTOR JOHN E. BECKER z/Mz M PATENT AGENTS March 1, 1966 BECKER 3,237,409

HYDRAULIC TURBO-COUPLINGS Filed April 6, 1964 I v 2 Sheets-Sheet 2 INVENTOR JOHN E.BECKER PATENT AGENTS 3,237,409 HYDRAULKC TURBO-COUPLINGS John E. Becker, Bowrnanvilie, ()ntario, Canada, assignor to Charles Robson, Oshawa, ()ntario, Canada Filed Apr. 6, 1964, Ser. No. 357,712 8 Claims. (Cl. 6054) This invention relates to hydraulic turbo-couplings of the type having a rotating working chamber comprising radially-vaned pump and turbine elements (otherwise commonly known as impeller and runner elements respectively), which elements cooperate With one another to form a toroidal working chamber for the contained liquid, and having means for varying automatically the degree of filling of the said working chamber to vary the torqueand power-transmission capacity of the coupling.

There is disclosed in the specification of my US. Patent No. 3,045,429 such a coupling in which the power-transmitting capacity can be controlled to be analogous to the power-producing capacity of a prime mover driving the pump element, and in which the torque-transmission capacity at stall can be controlled to be not greater than the maximum output torque of the said prime mover. In the coupling disclosed in my patent specification a reservoir chamber is provided rotatable With the work chamber and connected thereto by means which constantly circulate the working liquid between the two chambers under the influence of their rotation. The reservoir is divided into a plurality of compartments by spaced-apart bafile rings, in which compartments varying volumes of the working liquid are retained to vary the quantity of liquid in the working chamber. In the embodiment specifically described in that patent specification the means for varying the volume of the liquid retained in each of the said compartments comprises a respective drain pipe, the mouth of which is movable to the required level in the compartment under the control of a respective torsion bar, and an opposed, associated speed-responsive counter-weight, the radial distance of the mouth from the outer wall of the chamber determining the depth, and therefore the quantity, of the liquid in the chamber.

It is an object of the present invention to provide an improved hydraulic turbo-coupling of the type specified.

It is another object to provide a hydraulic turbo-coupling of the type specified comprising an improved means for the control of the filling of the Working circuit thereof.

It is a more specific object to provide a hydraulic turbocoupling of the type specified, and having a plurality of reservoir chambers with improved means for controlling the flow of working liquid between said chambers.

According to the present invention there is provided a hydraulic turbo-coupling comprising a radially-vaned pump element and a radially-vaned turbine element together defining a toroidal working chamber, a reservoir chamber rotatable with the pump element, bafile means providing in the interior of said reservoir chamber an analogising reservoir compartment having a predetermined maximum liquid volume, a stall reservoir compartment having a predetermined maximum liquid volume, and a further reservoir compartment, first port means connecting said analogising and stall compartments for flow of liquid between them, second port means connecting said stall and further compartments for flow of liquid between them, first and second duct means operative under the influence of rotation of the said pump element, said first duct means being operative to receive working liquid discharged from the working chamber and to deliever it to said analogising compartment, said second duct means being operative to withdraw working liquid from the said further compartment and to deliver it to the Working chamber, said duct and port means thereby establishing a working liquid circuit comprising in the order stated, the working chamber, the first duct means, the analogising compartment, the first port means, the stall compartment, the second port means, the said further compartment, the second duct means and the working chamber, first means responsive to a speed of rotation of the reservoir chamber above a predetermined value for closing the said first port means, and second means responsive to a speed of rotation of the reservoir chamber below a predetermined speed value for closing the said second port means.

A hydraulic turbo-coupling which is a particular preferred embodiment of the invention will now be described, by way of example, with reference to the accompanying diagrammatic drawings wherein:

FIGURES 1, 2 and 3 are similar sectional side elevations of the upper portion of the coupling, FIGURE 1 illustrating the operation of the coupling at a low speed of operation, FIGURE 2 illustrating the operation at a high speed, and FIGURE 3 illustrating the operation upon stalling of the turbine element,

FIGURES 4 and 5 illustrate the mode of operation respectively of the first and second port closing means,

FIGURE 6 shows in detail and to an enlarged scale the construction of either of the port closing means, and

FIGURE 7 illustrates an alternative detail of the construction of the port closing means.

As described before in my patent specification No. 3,045,429, and especially with respect to Figures 1 and 2 thereof, one of the disadvantages of a hydraulic turbocoupling containing a substantially constant volume of working liquid is that the torque-transmission capacity increases with increasing slip. With the turbine element completely stalled, which corresponds to slip, this capacity can amount to ten, fifteen or more times the value under normal operating conditions. For maximum efficiency the coupling should be designed to transmit the maximum torque output of the engine under normal conditions with only 2 or 3% slip, and consequently upon the existence of such stall conditions the coupling overloads the prime mover to an extent which is usually undesirable, and may even be suflicient to cause damage to the prime mover. Some improvement can be achieved by designing the coupling to have a slip of 5 or 6% under normal operating conditions, but the torque-transmission capacity under stall conditions usually is still too great for satisfactory operation, and in addition the relatively high slip causes a corresponding loss of power and the generation of large quantities of heat. This disadvantage is overcome in the couplings disclosed in my patent specification No. 3,045,429, and in couplings in accordance with the present invention, by providing that upon the existence of stall conditions in the turbine element enough working liquid is removed automatically from the working chamher to reduce the torque-transmission capacity of the coupling to substantially the same value as the maximum output torque of the prime mover, so that the latter can remain in operation at or very close to its speed at which it develops maximum torque.

Another disadvantage of a constant volume turbo-coupling is that its power-transmission capacity increases with increasing rotational speed more rapidly than the power output of an internal combustion engine used as the prime mover. For example, as shown by Figure 2 of my earlier specification, such a coupling designed to have 2% slip at 1800 rpm. will transmit all the power delivered to it by an internal combustion engine, but at 1400 rpm. the coupling Will only transmit 33 B.H.P. of the 50 B.H.P. delivered thereto by the engine, while at 2500 rpm. the coupling is able to transmit B.H.P. but can only be supplied with 85 B.H.P. by the engine. Consequently at the lower speeds there is excessive slip accompanied by excessive heating of the coupling and overloading of the engine, while at the higher speeds the slip is so low that the coupling fails to provide the required flexibility and does not fulfill the reason for its installation. This disadvantage is overcome in the couplings disclosed in my earlier patent specification, and also in couplings in accordance with the present invention, by providing means which are able automatically to control the filling of the working compartment to maintain the torquetransmission capacity of the coupling analogous to the power output capacity of the driving engine, thereby maintaining a relatively constant slip and resultant flexibility over the entire operating range of the driving engine.

Referring now to FIGURES 1 to 3, the coupling illustrated therein comprises a pump element It) with radial vanes 11 and having a drive stub-shaft 12 adapted for connecting the element to a prime mover (not shown), such as an internal combustion engine. A turbine element with radial vanes 14 is mounted on a shaft 15 for rotation relative to the pump element, the shaft 15 having its inner end carried by a bearing 16 (which bearing is in turn carried by the pump element llil) and being adapted for connecting the coupling to a member to be driven thereby. A cylindrical liquid reservoir 17 is rigidly connected to the pump element for rotation therewith, and has its axially outer end carried by a bearing 18 mounted on the shaft 15. A shroud casing 19 is rigid with the reservoir casing and extends closely around the outer surface of the turbine casing to provide an annular shroud chamber 2t} that communicates with the reservoir interior through a ring of holes such as 21 in the radially outermost part of the shroud. The reservoir interior is provided with an annular partition 22 and two annular bafiies 23 and 24, which separate the said interior into what are called, for convenience in nomenclature, an analogising compartment 25 between the baffle 23 and the adjacent reservoir end wall, a stall compartment 26 between the two bailies, a reservoir pick-up compartment 27 between the partition 22 and the baffle 24 and a pump pick-up compartment 23 between the partition 22 and the shroud 19.

A first duct means 29 is mounted on a stationary sleeve Stl surrounding the shaft 15 and comprises a liquid scoop having an inlet 31 for liquid from the pump pick-up compartment 28 and an outlet 32 delivering the liquid along the reservoir end wall into the analogising compartment 25. A second duct means 33 is also mounted on the sleeve 3t? and comprises a liquid scoop having an inlet 34 for liquid from the reservoir pick-up compartment 27 and an outlet 35 delivering the liquid via an inlet 36 in the turbine element wall into the coupling working circuit. First port means are provided in the baffle 23 connecting the interiors of the analogising and stall compartments, and normally comprise at least one circular row of apertures 37; in the embodiment illustrated such means comprise two such rows. Also in this embodiment all of the apertures 37 are of the same diameter, all of the apertures of the same row are spaced the same radial distance from the coupling rotational axis, and the two rows are spacedat ditferent distances from the said axis for a purpose described hereinafter. The stall and reservoir pickup compartments are connected by second port means constituted by a single circular row of apertures 38 in the battle 24. In this embodiment all of the apertures 38 are of the same diameter and all are spaced the same radial distance from the coupling rotational axis.

It will now be seen that there exists in the coupling a working liquid flow circuit comprising, in the order named, a working chamber, the holes 21, the compartment 28, the first duct means 29, the analogising compartment 25, the apertures 37 of the first port means, the stall compartment 26, the apertures 38 of the second port means, the chamber 27, the second duct means 33, the inlet 36 and the Working chamber again.

The edges 3? and 40 respectively of the central bores in the shroud 19 and the partition 22 both have slightly smaller diameters than the internal diameter of the working compartment, so that any overfilling of the associated compartments will result in spilling of the liquid into the working chamber or the remainder of the reservoir. The edges 41 and 42 respectively of the central bores in the baffles 23 and 24 are at the minimum diameter contemplated for a coupling of the size in which they are incorporated, and, if for a specific embodiment the baflles are too deep and too much liquid is retained in the associated compartments, this is remedied by providing a row of spill holes at the required radial distance from the coupling axis, the spill holes for the bafiles 23 and 24 being indicated respectively by 43 and 44, the liquid levels which such holes determine being indicated in FIGURES 4 and 5 by the broken lines 45 and 46 respectively.

Referring specifically to FIGURE 1, it will be seen that this illustrates the slow condition of operation of the coupling over the range of speeds at which the coupling power-transmission capacity is analogous to the power output capability of the prime mover. Under this condition the reservoir compartments all contain their minimum quantities of liquid, while the working chamber contains its maximum quantity, it being noted that the flow capacities of the first and second port means and the second duct means are all appreciably greater than that of the first duct means.

Each aperture 37 of the first port means is provided with an associated closure member 47, which is automatically movable radially inwardly upon an increase in the rotational speed of the pump element and the reservoir to progressively close the aperture and thereby increase the quantity of liquid retained in the analogising compartment, as illustrated by FIGURE 2. As more liquid is retained in the analogising compartment less liquid is available for the working circuit and the power-transmission capacity of the coupling drops and its slip increases, as is desired for the reasons described above. By correlation of the degree of closing of the apertures 37 with the rotational speed of the coupling, the power-transmission capacity of the coupling at any speed can be maintained analogous to the power available from the prime mover at that speed, over a wide range of such speeds. In the embodiment illustrated a single row of holes is not able to provide a power-transmission control that is sufficiently wide and precise, and accordingly over the lower speeds of the range the control is provided by controlled closure of the radially outer apertures, while over the higher speeds the last-mentioned apertures are fully closed and the control is effected by controlled closure of the radially inner apertures. It will be seen from FIGURE 4 that, in a practical embodiment, there must be an overlap between the two rows of apertures to provide a smooth transition of control. It will also be appreciated that in other embodiments other arrangements of the apertures may be provided, e.g., single or multiple-start spirals, and the apertures may be of different diameters to provide a desired analogising control characteristic.

Each aperture 38 of the second port means is provided with an associated closure member 48, which is automatically movable radially outwardly upon a decrease in rotational speed of the pump element below a predetermined level, such as would be produced by the existence of an undesirably large stalling load applied to the turbine element. As shown by FIGURE 3, both the analogising and the stall compartments must now be filled before liquid can escape through the spill holes 44 into the pick-up compartment, and the arrangement is such that the volume of liquid remaining in the working chamber is only able to provide a torque-transmission capability substantially equal to the maximum output torque of the prime mover. Under such conditions therefore the prime mover is able to continue rotation at the speed at which it is able to produce maximum torque (with full or wide-open throttle setting in the case of an internal combustion engine) without overloading of itself or the coupling, until the stall condition has been removed, when the normal conditions illustrated by FIGURE 1 are restored.

It may be noted that although the compartment 26 is referred to herein as the stall compartment, in this particular embodiment this is not a precise description of its function, since under stall conditions the liquid removed from the working circuit is stored in both the stall and the analogising compartments, the latter compartment thus performing two functions. Such an arrangement has the advantage that the volume required for the stall compartment is reduced by the volume of the analogising compartment, resulting in a more compact coupling construction. It is also envisaged that in other embodiments the two compartments may perform their functions independently of one another, being operative in parallel and not in series as in the described embodiment. In such a parallel arrangement the duct means 29 deliver liquid simultaneously to both the stall and analogising compartments and the respective closable port means connect their compartments in parallel to the pickup compartemnt 27. For example, the port means 37 may comprise a duct that leads directly from the compartment 25, through the compartment 26 and discharges into the compartment 27.

Reference will now be made to FIGURES 4 to 7 in describing a particular preferred construction of closure member and means for controlling the member. As shown by FIGURES 4 and 5, the closure members 47 and 48 respectively are each mounted at one end of arm 49, the other end of which is pivotally mounted on the respective bafile and carries a counterweight 50. In each case the effective Weight of the counterweight is greater than that of the arm, so that the arms rotate clockwise as seen in the figures upon an increase in rotational speed of the reservoir. Referring specifically to FEGURE 6, it will be seen that each arm 49 and counter-weight Stl are fixed to and rotatable with a hollow cylindrical member 51 that is rotatably mounted by bearings 52 in the interior of another such member 53. The member 53 is mounted by a tubular bracket 54 in the associated baffie 23 or 24 and has fixed to one end thereof one end of an arm 55. The other end of the arm 55 carries a tube 56 engaged in a larger tube 57 that is in turn mounted in the asso ciated bafile 23 or 24, the tubes providing the respective port apertures 37 or 33. The tubular members 51 and 53 are connected by a torsion bar 58 that has its ends 59 of non-circular cross-section and engaged in corresponding non-circular apertures in the members. It will be seen that the speed control characteristic will depend upon the difference in effective weights of the arm 49 and the counter-weight 50, and also upon the characteristics of the torsion bar 58. Such a construction has the very substantial commercial advantage that a wide range of speed control characteristics can be obtained by suitable choice of the counter-weight and the torsion bar only, and all the other parts can be standard for a Wide range of coupling sizes. It may also be noted that the items 49 to 57 can all be die cast by mass production methods.

Two tubes 56 and 57 are employed to provide the port apertures 37 or 38, since the battle in which the tube 57 is mounted may deflect to an extent that changes with the level of the working liquid in the associated compartments, disturbing the seating between the tube and a closure member engaging directly with the tube 57. Increasing the rigidity of the battle will, in general, increase the Weight and cost of the coupling, and instead the two tubes form a flexible joint, being provided with a loosely-fitting O-ring oil between them to prevent leakage, that will accommodate any such misalignment of the tube 57. Another advantage of the construction is that the parts 47 to 53, 55, 56, 58 and 59 together constitute a control sub-assembly that can be pre-assembled, adjusted and tested apart from the coupling, and can be assembled into and removed therefrom as required as a single unit.

FIGURE 7 illustrates a modification of the arrangement of FIGURE 6, in which the mating faces of the closure members 47, 48 and the tube 56 are inclined at a slight angle (much exaggerated in the figure for clarity of illustration), so that the members are only fully engaged when in the fully closed position, thereby permitting closure without appreciable sliding friction until they are almost fully closed, when the liquid flow is small and such friction can no longer have an appreciable effect on the rotational speed/closing characteristic. In other embodiments the closure mmebers 47 and 48 may be of constant thickness, while the tube 56 has its longitudinal axis inclined at the necessary small angle.

What I claim is:

1. A hydraulic turbo-coupling comprising a radiallyvaned pump element and a radially-vaned turbine element together defining a toroidal working chamber, a substantially cylindrical reservoir chamber coaxially positioned with respect to the toroidal work chamber and rotatable with the pump element, bafile means in the interior of said reservoir chamber extending radially inwards from the interior of the reservoir cylindrical wall to provide an analogising reservoir compartment having a predetermined maximum liquid volume, a stall reservoir compartment having a predetermined maximum liquid volume and a further reservoir compartment, the said compartments being of annular form and adapted to retain liquid while in a centrifugal ring, first port means connecting said analogising and stall compartments for flow of liquid between them, second port means connecting said stall and further compartments for flow of liquid between them, first and second duct means operative under the in-, fiuence of rotation of the said pump element to pick up working liquid from an area radially remote from the axis of rotation of the coupling and exhaust it nearer to the said axis, said first duct means being operative to receive working liquid discharged from the working cham bet and to deliver it to the said analogising compartment, said second duct means being of larger liquid transfer capaoity than said first duct means and being operative to withdraw working liquid from the said further compartment and to deliver it to the working chamber, said duct and port means thereby establishing a working liquid circuit comprising in the order stated, the working chamber, the first duct means, the analogising compartment, the first port means, the stall compartment, the second port means, the said further compartment, the second duct means and the working chamber, first closure means responsive to a speed of rotation of the reservoir chamber above a predetermined value for closing the said first port means, and second closure means responsive to a speed of rotation of the reservoir chamber below a predetermined speed value for closing the said second port means.

2. A coupling as claimed in claim 1, wherein the said first and second closure means comprise a closure member associated with each port of the corresponding port means, a pivoted lever arm for each closure member mounting the member for pivoting movement about the lever arm pivot in response to change of rotational speed of the coupling reservoir, means mounting the lever arm for such movement, and a torsion member operatively connected between the lever arm and its mounting means and determining the rotational speed/port closing characteristics of the respective closure member.

3. A hydraulic turbo-coupling comprising a radiallyvaned pump element and a radially-vaned turbine element together defining a toroidal working chamber, a substantially cylindrical reservoir chamber coaxially positioned with respect to the toroidal work chamber and rotatables with the pump element, bafile means in the interior of said reservoir chamber extending radially inwards from the interior of the reservoir cylindrical wall to provide an analogising reservoir compartment having a predetermined maximum liquid volume, a stall reservoir compartment having a predetermined maximum liquid volume and a further reservoir compartment, the said compartments being of annular form and adapted to retain liquid while in a centrifugal ring, first port means connecting said analogising and stall compartments for flow of liquid between them, second port means connecting said stall and further compartments for flow of liquid between them, first and second duct means operative under the influence of rotation of the said pump element to pick up working liquid from an area radially remote from the axis of rotation of the coupling and exhaust it nearer to the said axis, said first duct means being operative to receive working liquid discharged from the Working chamber and to deliver it to the said analogising compartment, said second duct means being of larger liquid transfer capacity than said first duct means and being operative to withdraw working liquid from the said further compartment and to deliver it to the working chamber, said duct and port means thereby establishing a working liquid circuit comprising in the order stated, the working chamber, the first duct means, the analogising compartment, the first port means, the stall compartment, the second port means, the said further compartment, the second duct means and the Working chamber, first closure means responsive to a speed of rotation of the reservoir chamber above a predetermined range of values for closing the said first port means progressively over another increasing range of values higher than the said predetermined range, and sec-. ond closure means responsive to a speed of rotation of the reservoir chamber below a predetermined speed value for closing the said second por-t means.

4. A coupling as claimed in claim 3, wherein the said first port means comprise a plurality of passages in the respective baflie with different ones of the passages disposed at least two diiferent radial positions, and the said first closure means comprise a respective closure memberfor each aperture, the closure members at the radially outer positions being responsive for closing the associated passage at a lower rotational speed than the closure members at the radially inner positions.

5. A coupling as claimed in claim 3, wherein the said first and second closure means comprise a closure member associated with each port of the corresponding port means, a pivoted lever arm for each closure member mounting the member for pivoting movement about the lever arm pivot in response to change of rotational speed of the coupling reservoir, a counter-weight operatively connected to the pivoted lever arm and movable in re sponse to change of speed of the coupling reservoir in the sense to prevent said pivoting movement of the arm In response to such change, means mounting the lever arm and the counter-weight for the said speed responsive movement, and a torsion member operatively connected between the lever arm, the counter-weight and their mountlng means and determining the rotational speed/ port closing characteristic of the respective closure mem- 6. A hydraulic turbo-coupling comprising a radially vaned pump element and a r-adially-vaned turbine element together defining a toroidal working chamber, a substantially cylindrical reservoir chamber coaxially positioned with respect to the toroidal work chamber and. rotatable with the pump element, a partition in the reservoir chamber extending radially inwards from the interior of the reservoir cylindrical wall and providing a pick-up compartment of annular form adapted to retain liquid while in a centrifugal ring between itself and the turbine element, a first bafiie means in the reservoir and providing a further compartment between itself and the partition, a second baifie means in the reservoir and providing a stall compartment between itself and the first bafiie means, and providing an analogising compartment between itself and the remainder of the reservoir chamher, the said first and second baffie means also extending radially inwards from the interior of the reservoir S cylindrical wall, and the said further, stall and analogising compartments also being of annular form adapted to retain liquid while in a centrifugal ring, flow means connecting the interiors of the working chamber and the said pick-up compartment, first port means connecting said analogising and stall compartments for flow of liquid between them, second port means connecting said stall and furtherpompartments for fiow of liquid between them, first and second duct means operative under the influence of rotation of the said pump element to pick up working liquid from an area radially remote from the axis of rotation of the coupling and exhaust it nearer to the said axis, said first duct means comprising scoop means removing working liquid from said pick-up compartment and delivering it to said analogising compartment, said second duct means being of larger liquid transfer capacity than said first duct means and comprising scoop means removing working liquid from said further compartment and delivering it to the working chamber, said duct and port means thereby establishing a working liquid circuit comprising in the order stated, the Working chamber, the pick-up chamber, the first duct means, the analogising compartment, the first port means, the stall compartment, the second port means, the said further compartment, the second duct means and the working chamber, first closure means responsive to a speed of rotation of the reservoir chamber above a predetermined range of values for closing the said port means progressively over another increasing range of values higher than the said predetermined range, and second means responsive to a speed of rotation of the reservoir chamber below a predetermined speed value for closing the said second port means.

7. A hydraulic turbo-coupling comprising a radiallyvaned pump element and a radially-vaned turbine element together defining a toroidal working chamber, a substantially cylindrical reservoir chamber coaxially positioned with respect to the toroidal w-ork chamber and rotatable with the pump element, baffle means in the interior of said reservoir chamber extending radially inwards from the interior of the reservoir cylindrical wall to provide an analogising reservoir compartment having a predetermined maximum liquid volume, a stall reservoir compartment having a predetermined maximum liquid volume and a further reservoir compartment, the said compartments being of annular form and adapted to retain liquid while in a centrifugal ring, first port means connecting said analogising and further compartments for flow of liquid between them, second port means connecting said stall and further compartments for flow of liquid between them, first and second duct means operative under the influence of rotation of the said pump element to pick up working liquid from an area radially remote from the axis of rotation of the coupling and exhaust it nearer to the said axis, said first duct means being operative to receive working liquid discharged from the working chamber and to deliver it to the said analogising and stall compartments, said second duct means being of larger liquid transfer capacity than said first duct means and being operative to withdraw working liquid from the said furthcr compartment and to deliver it to the working chamher, said duct and port means thereby establishing a first working liquid circuit comprising in the order stated, the working chamber, the first duct means, the analogising compartment, the first port means, the said further com partment, the second duct means and the working chamber, and a second working circuit comprising in the order stated, the working chamber, the first duct means, the stall compartment, the second port means, the said further compartment, the second duct means and the Working chamber, first closure means responsive to a speed of IO- tation of the reservoir chamber above a predetermined value for closing the said first port means, and second closure means responsive to a speed of rotation of the reservoir chamber below a predetermined speed value for closing the said second port means.

8. A coupling as claimed in claim 7, wherein said first. closure means are responsive to a speed of rotation of the, reservoir chamber above a predetermined range of values for closing the said first port means progressively over another increasing range of values higher than the said predetermined range, and the said second closure means are responsive to a speed of rotation of the reservoir References Cited by the Examiner UNITED STATES PATENTS 3,045,429 7/1962 Becker 60-54 JULIUS E. WEST, Primary Examiner. 

1. A HYDRAULIC TURBO-COUPLING COMPRISING A RADIALLYVANED PUMP ELEMENT AND A RADIALLY-VANED TURBINE ELEMENT TOGETHER DEFINING A TOROIDAL WORKING CHAMBER, A SUBSTANTIALLY CYLINDRICAL RESERVOIR CHAMBER COAXIALLY POSITIONED WITH RESPECT TO THE TOROIDAL WORK CHAMBER AND ROTATABLE WITH THE PUMP ELEMENT, BAFFLE MEANS IN THE INTERIOR OF SAID RESERVOIR CHAMBER EXTENDING RADIALLY INWARDS FROM THE INTERIOR OF THE RESERVOIR CYLINDRICAL WALL TO PROVIDE AN ANALOGISING RESERVOIR COMPARTMENT HAVING A PREDETERMINED MAXIMUM LIQUID VOLUME, A STALL RESERVOIR COMPARTMENT HAVING A PREDETERMINED MAXIMUM LIQUID VOLUME AND A FURTHER RESERVOIR COMPARTMENT, THE SAID COMPARTMENTS BEING OF ANNULAR FORM AND ADAPTED TO RETAIN LIQUID WHILE IN A CENTRIFUGAL RING, FIRST PORT MEANS CONNECTING SAID ANALOGISING AND STALL COMPARTMENTS FOR FLOW OF LIQUID BETWEEN THEM, SECOND PORT MEANS CONNECTING SAID STALL AND FURTHER COMPARTMENTS FOR FLOW OF LIQUID BETWEEN THEM, FIRST AND SECOND DUCT MEANS OPERATIVE UNDER THE INFLUENCE OF ROTATION OF THE SAID PUMP ELEMENT TO PICK UP WORKING LIQUID FROM AN AREA RADIALLY REMOTE FROM THE AXIS OF ROTATION OF THE COUPLING AND EXHAUST IT NEARER TO THE SAID AXIS, SAID FIRST DUCT MEANS BEING OPERATIVE TO RECEIVE WORKING LIQUID DISCHARGED FROM THE WORKING CHAMBER AND TO DELIVER IT TO THE SAID ANALOGISING COMPARTMENT, SAID SECOND DUCT MEANS BEING OF LARGER LIQUID TRANSFER CAPACITY THAN SAID FIRST DUCT MEANS AND BEING OPERATIVE TO WITHDRAW WORKING LIQUID FROM THE SAID FURTHER COMPARTMENT AND TO DELIVER IT TO THE WORKING CHAMBER, SAID DUCT AND PORT MEANS THEREBY ESTABLISHING A WORKING LIQUID CIRCUIT COMPRISING IN THE ORDER STATED, THE WORKING CHAMBER, THE FIRST DUCT MEANS, THE ANALOGISING COMPARTMENT, THE FIRST PORT MEANS, THE STALL COMPARTMENT, THE SECOND PORT MEANS, THE SAID FURTHER COMPARTMENT, THE SECOND DUCT MEANS AND THE WORKING CHAMBER, FIRST CLOSURE MEANS RESPONSIVE TO A SPEED OF ROTATION OF THE RESERVOIR CHAMBER ABOVE A PREDETERMINED VALUE FOR CLOSING THE SAID FIRST PORT MEANS, AND SECOND CLOSURE MEANS RESPONSIVE TO A SPEED OF ROTATION OF THE RESERVOIR CHAMBER BELOW A PREDETERMINED SPEED VALUE FOR CLOSING THE SAID SECOND PORT MEANS. 